An electromyographic study of masticatory and lip muscle function in patients with complete dentures

The activity of the anterior and posterior portions of the temporal muscle, of the masseter muscle, and of the upper and lower lips was studied with electromyography in 10 individuals with complete dentures. Recordings were made when the patients had old, ill-fitting dentures and 6 months after these were replaced with new dentures. The muscle activity was studied in the postural position of the mandible, during chewing and swallowing of three test foods, and during maximal biting. The maximal tooth tapping rate was also recorded. The postural muscle activity was the same with old and new dentures and comparable with that in patients with natural teeth. The muscle activity during maximal biting was markedly lower than in patients with natural teeth and lower with new than with old dentures. There was no difference in muscle activity between chewing with old and new dentures, but the activity was lower than in patients with natural teeth. This was not compensated for by a longer duration of chewing. The lips were not especially active during chewing in the complete denture wearers.